Technical Field
The present disclosure relates to a solid-supported catalyst ligand and palladium (II) complexes and catalyst compositions thereof. Additionally, the present disclosure relates to methods for producing the solid-supported catalyst ligand and methods employing its complexes to catalyze chemical transformations including palladium cross-coupling reactions.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Catalytic cross coupling reactions have been recognized among the best direct routes for the formation of carbon-carbon bonds [G. Zhang, Y. Luan, X. Han, Y. Wang, X. Wen, C. Ding, Appl. Organomet. Chem. 2014, 28, 332.—incorporated herein by reference in its entirety]. Palladium complexes have been the most effective and versatile catalysts for the synthesis of biphenyls (Suzuki-Miyaura cross coupling reactions), internal alkenes, and alkynes (Mizoroki-Heck and Sonogashira cross coupling reactions) [H. U. Blaser, A. Indolese, A. Schnyder, H. Steiner, M. Studer, J. Mol. Cat. A: Chem. 2001, 173, 3; and G. A. Orasa, M. S. Viciu, J. Huang, C. Zhang, M. L. Trudell, S. P. Nolan, Organomet. 2002, 21, 2866; and L. Yin, J. Liebscher, Chem. Rev. 2007, 107, 133; and F. X. Felpin, T. Ayad, S. Mitra, Eur. J. Org. Chem. 2006, 2679; and C. Lui, F. Bao, Q. Ni, Arkivoc xi, 2011, 60; and J. T. Guan, T. Q, Weng, G. Yu, S. H. Liu, Tetrahedron Lett. 2007, 48, 7129; and A. Komaromi, Z. Novak, Chem. Comm. 2008, 4968; and H. Huang, H. Liu, H. Jiang, K. Chen, J. Org. Chem. 2008, 73, 6037; and Z. Gu, Z. Li, Z. Liu, Y. Wang, C. Liu, J. Xiang, Catal. Comm, 2008, 9, 2154; and M. A. Casado, A. Fazal, L. A. Oro, Arab. J. Sc. Eng., 2013, 38, 1631; and G. K. Rao, A. Kumar, S. Kumar, U. B. Dupare, A. K. Singh, Organomelallics, 2013, 32, 2452; and T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147.—each incorporated herein by reference in its entirety]. The products of these cross coupling reactions are extensively used in the production of important industrial raw materials, pharmaceutical and biologically active molecules [M. Toyota, C. Komori, M. J. Ihara, Org. Chem. 2000, 65, 7110; and G. Amiet, H. M. Hugel, F. Nurlawis, Synlett. 2002, 3, 495.—each incorporated herein by reference in its entirety]. The ability of palladium complexes to function effectively as catalysts for cross coupling reactions has been attributed to the feasible and facile interchange between Pd(0) and Pd(II) or Pd(II) and Pd(IV). Plenty of homogeneous palladium complexes have been described to successfully catalyze various cross coupling reactions with high selectivity, high activity, and low catalyst loading. The complete removal of homogeneous catalysts from the cross coupling products is a complex and costly process, thus reducing the chances of industrial implementation since metal contamination in the end products is highly modulated by the pharmaceutical and related industries [V. Polshettiwar, C. Len, A. Fihri, Coord. Chem. Rev. 2009, 253, 2599. —incorporated herein by reference in its entirety].
A suitable method of overcoming the separation problem is immobilizing the homogeneous catalyst [H. Gruber-Woelfler, P. F. Radaschitz, P. W. Feenstra, W. Haas, J. G. Khinas, J. Catal. 2012, 286, 30.—incorporated herein by reference in its entirety]. Other than easy removal from the coupling products, the immobilized catalyst offers the potential of recycling and the possibility of for use in a continuous flow reactor [K. Hallamn, C. Mobcrg, Tetrahedron: Asymmetry, 2001, 12, 1475.—incorporated herein by reference in its entirety]. The ability to separate and reuse the supported catalyst makes it a more viable alternative, especially from an economical point of view. As a result of these substantial advantages, the interest in the use of immobilized palladium catalysts to catalyze cross coupling reactions has been increasing rapidly. Although several supported palladium catalysts have been reported, the application of supported palladium bis(oxazoline) complex catalysts in cross coupling reactions has not been widely explored.
In practice, the separation of the supported catalysts from the products is done either by decantation or by filtration. In these separation techniques, the recovery of all the catalyst is unlikely, and the decrease in reaction rate observed in the latter cycles of most supported catalytic systems is rarely due to catalyst deactivation, but rather is largely due to the inability to recover all of the catalyst during separation. Attempts have been made to simplify the recovery of the catalyst. These include, but are not limited to, applying biphasic reaction conditions, the use of sol gels, and membrane reactors [S. K. Karmee, C. Roosen, C. Kohlmann, S. Lutz, L. Greiner, W. Leitncr, Green Chem. 2009, 11, 1052; and F. Gelman, J. Blum, D. Avnir, J. Am. Chem. Soc. 2000, 122, 11999; and L. Canatarella, A. Gallifuoco, A. Malandra, L. Martinkova, A. Spera, M. Cantarella, Enzyme Microb. Technol. 2011, 48, 345. —each incorporated herein by reference in its entirety].
Another way of aiding catalyst recovery is to contain the catalysts in a semipermeable membrane. The membrane that is required for this technique is designed to allow easy transportation of both reactants and products and have a pore size that guarantees retenction of the catalyst. This design makes it possible to recover all of the catalyst after each catalytic run. The semipermeable membrane should also be compatible with all of the reaction conditions including the reactants, solvents, temperatures and pressures. The driving force in many of these reactions is usually temperature, pressure or concentration gradient [I. F. J. Vankelecom, Chem. Rev. 2002, 102, 3779; and M. Gaab, S. Bellemin-Laponnaz, L. H. Gade, Chem. Eur. J. 2009, 15, 5450.—each incorporated herein by reference in its entirety].
In view of the forgoing, one object of the present disclosure is to provide a solid-supported catalyst ligand having suitable functionality for coordinating palladium (II) and a heterogeneous solid-supported palladium (II) catalyst thereof, such as a Merrifield resin supported palladium bis(oxazoline) catalyst. A further aim or the present disclosure is to provide methods for preparing the solid-supported catalyst ligand and solid-supported palladium (II) catalyst as well as methods employing the solid-supported catalyst in palladium cross-coupling reactions, such as, a Suzuki-Miyaura reaction, a Mizoroki-Heck reaction, and a Sonogashira reaction, demonstrating significant catalytic activity and recycling ability.